Cardiac stents, which are an example of a self-expanding device, are inserted into a blood vessel to provide an open path within the blood vessel, have been widely used in intravascular angioplasty treatment of occluded cardiac arteries, and in other applications. Stents are often deployed by use of inflatable balloons, or mechanical devices which force the stent open, thereby reinforcing the artery wall and provide a clear through-path in the center of the artery after the angioplasty procedure to prevent restenosis. The use of placement techniques, such as balloons or mechanical expansions of the type often found to be useful in cardiac surgery, are relatively less useful in vasoocclusive surgery, particularly when tiny vessels, such as those found in the brain, are to be treated.
Other stents are self expanding and are just deployed inside of the vascular. Their self-expanding nature allows them to be smaller as well as the devices to deploy them. There are different techniques to deploy the stents, and each has benefits and drawbacks. One expandable stent and delivery system is known that includes an expandable stent having proximal and distal anchor members mounted on proximal and distal legs extending proximally and distally from the stent. The proximal and distal anchor members of the expandable stent are mounted in gaps formed between proximal, intermediate and distal cylindrical members disposed on and spaced apart along an elongated core member. However, pushing the device distally in a catheter from the proximal end of the device is not optimal, because application of force in a distal direction on the proximal end of the stent can axially compress the stent, and can cause the stent to expand radially. Likewise, retracting the device proximally may not be optimal either, because application of force in a proximal direction on the distal end of the stent also can axially compress the stent, and can cause the stent to expand radially.
The deployment techniques fall into two categories, one is where the members are deployed outside the stent to pull or push accordingly depending on distal or proximal placement, or sometimes both. See, U.S. Pat. Nos. 6,123,723, 6,280,465, and US Publication No. 2011/0307049. Other techniques deploy the members inside of the stent. See, US Publication No. 2014/0277360, and U.S. Pat. Nos. 5,702,418, and 6,955,685. However, self-expanding device delivery systems with multiple members pose two problems:
1) After the physician has deployed the self-expanding device, he/she must re-sheathe the delivery wire back into the microcatheter, to then dispose of the wire. When recapturing the delivery wire, the members of the delivery system can get caught on the deployed device, and can subsequently alter the position of the device in the anatomy. The more members on the wire, the more often this can happen.
2) The more members on the delivery wire, the more difficult it is to manufacture. In order to build the delivery system, a manufacturer can either secure polymer/metal sleeves onto a core wire, or grind down a core wire to create members on a wire. The more members on a delivery wire, the more material must be used to add and secure members, or, the more the grind profile has to change to accommodate all of the members.
Thus, would be desirable to provide a delivery system for expandable stents that offers the flexibility of engaging the device and for pushing and/or pulling the device proximally or distally as desired. Also desirable is a simplified manufacturing method.